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Re: [mdb-dev] Success - kind of...
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From: Andreas R. <mdb...@ri...> - 2005-10-03 13:14:16
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I can find some of the code, but don't have access from it at my current
location...
Basically mdb_bind_column to a buffer of size MDB_BIND_SIZE
Then after fetching the row. Copy this data into a size MDB_MEMO_OVERHEAD
and use the new buffer in the call to mdb_read_ole. This call will then copy
the data into the original bound buffer and return the size for you. Copy
that data into yet another buffer. Then call mdb_read_ole_next to see if
there is more data. If there is it will again be copied to the bound buffer.
You can append it to the data you already stored away. Then call
mdb_read_ole_next again until it returns 0. I'll paste some code here when I
get home tonight.
There is one little snippet of code in the sources that also uses
mdb_read_ole. That's where I figured out how to use this. Just grep for
mdb_read_ole in all the sources.
Thanks,
Andy
----- Original Message -----
From: "Shanon Mulley" <sha...@gm...>
To: "Brian A. Seklecki" <lav...@sp...>
Cc: "Andreas Richter" <mdb...@ri...>; "Sam Moffatt"
<pa...@gm...>; <mdb...@li...>
Sent: Monday, October 03, 2005 8:23 AM
Subject: Re: [mdb-dev] Success - kind of...
Andreas,
You seem to be having more success with reading binary data from
access then myself. I'm wondering if you can give me a few pointers
with getting binary data out. I've been teaching myself how to use
mdbtools, but am yet to work this out. You mention a command
"mdb_read_ole". Can you tell me where this is used?
I'm using the latest version (from cvs), but didnt enable odbc - that
wouldnt make properly.
Thanks.
On 10/3/05, Brian A. Seklecki <lav...@sp...> wrote:
> Specifically which versions of the autotools did you use, just out of
> curiosity?
>
> ~BAS
>
> On Fri, 2005-09-30 at 20:59, Andreas Richter wrote:
> > Hi,
> > After beating autoconf, libtool, autogen and so on into pulp I have the
> > CVS
> > version running. It can correctly read the blobs with mdb_read_ole!!!
> > Yes.
> > However blobs that are longer than will cause an segment fault in
> > mdb_read_ole_next. The problem seems to be that the length calculation
> > is
> > wrong. The following code in mdb_find_pg_row comes back with a len of
> > 0xfffffb9b i.e. A negative number.
> >
> > mdb_swap_pgbuf(mdb);
> > mdb_find_row(mdb, row, off, len);
> > mdb_swap_pgbuf(mdb);
> >
> > In mdb_find_row the next_start is 4096 even though I am not loading the
> > blob
> > from the first row. By testing thing I think I figured out that
> > sometimes
> > blobs come with extensions, but the pg_row for the extension (i.e. The
> > next
> > pointer) is zero. Therefore making the following change in
> > mdb_read_ole_next
> > seemed to fix the crash (line 460)
> >
> > if (mdb_find_pg_row(mdb, col->cur_blob_pg_row,
> > &buf, &row_start, &len)) {
> > return 0;
> > }
> >
> > To
> >
> > if (!col->cur_blob_pg_row || mdb_find_pg_row(mdb,
> > col->cur_blob_pg_row,
> > &buf, &row_start, &len)) {
> > return 0;
> > }
> >
> > BTW: The CVS version of mdbtools.h has an #include <config.h> which
> > probably
> > won't work from a normal include directory.
> > Thanks,
> > Andy
> >
> > > From: Andreas Richter <mdb...@ri...>
> > > Date: Fri, 30 Sep 2005 11:24:31 -0400
> > > To: 'Sam Moffatt' <pa...@gm...>, 'Andreas Richter'
> > > <mdb...@ri...>
> > > Cc: <mdb...@li...>
> > > Subject: RE: [mdb-dev] Problem reading blobs
> > >
> > > No success building CVS dump under Darwin. The 0.6pre tar file did
> > > work
> > > correctly under a fink installation, but the autogen.sh file for the
> > > CVS
> > > dump did not work. Has anyone done this yet? I'll probably just
> > > execute the
> > > autogen.sh under linux and then move the files to Darwin. Any
> > > suggestions
> > > would be great.
> > > Thanks,
> > > Andy
> > >
> > > -----Original Message-----
> > > From: Sam Moffatt [mailto:pa...@gm...]
> > > Sent: Thursday, September 29, 2005 8:17 AM
> > > To: Andreas Richter
> > > Cc: mdb...@li...
> > > Subject: Re: [mdb-dev] Problem reading blobs
> > >
> > > what version of the library and as others will say, the cvs version
> > > has heaps of improvements in it.
> > >
> > > On 9/29/05, Andreas Richter <mdb...@ri...> wrote:
> > >>
> > >>
> > >> Hi,
> > >>
> > >> I am trying to read an access 2k database with blobs. After reading
> > >> the
> > > blob
> > >> with mdb_read_ole it will give me a 4k of data. Calling
> > >> mdb_read_ole_next
> > >> will always tell me that there is no more data. Is mdb_read_ole
> > >> currently
> > >> implemented for normal blobs? Can I help implementing it? I am using
> > >> the
> > >> library under Mac OS X.
> > >>
> > >> Thanks
> > >>
> > >> Andy
> > >>
> > >
> >
> >
> >
> >
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>
>
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